Silencer or muffler



y 1958 F. E. DEREMER 2,835,336

SILENCER 0R MUFFLER Filed July 15, 1953 7 2 Sheets-Sheet 1 INVENTOR. FLOYD E.DEREMER May 20, 1958 F. E. DEREMER SILENCER OR MUFFLER Filed July 15, 1953 2 Sheets-Sheet 2 INVENTOR. FLOYD 'E.DEREMER BY ATT'Y the operation of an internal-combustion engine.

SILENCER on MUFFLER Floyd E. Deremer, Detroit, Mich, assignor to Oldberg Manufacturing Company, Grand Haven, Mich., a corporation of Michigan Application July 15, 1953, Serial No. 358,045

12 Claims. (Cl. 181-61) This invention relates to method andapparatus for attenuating sound waves and, more especially, to silencers or mufflers for attenuation of sound waves entrained in streams of exhaust gases in exhaust systems of internalcombustion engines, particularly exhaust systems of en gines used in automotive vehicles.

Silencing devices have been used with exhaust systems of internal-combustion engines and with other moving gas streams for attenuating sound waves entrained in the gas stream to minimize or reduce the sound or noise attendant The interior construction of a conventional mufller or silencer usually consists of an arrangement of gas passage tubes associated with resonating or sound-attenuating chambers and baflie means for interrupting, clamping or attenuating sound waves with the least possible back-pressure of the gas stream. It is a practice in sound-attenuating mufiler constructions to utilize tubes and other elements provided with perforations forming acoustic couplings between gasconveying passages or tubes and sound-attenuating chambers, and such arrangements are effective to attenuate sound waves entrained in a moving gas stream.

Mufiler constructions of conventional character have been provided with a single wall shell or casing or a laminated shell wherein the laminations were in continuous contact absent any space between the laminations. The muffier shell or casing forms wall portions of resonance or sound-trap chambers and is subjected to vibrations under the influence of impinging sound waves.

These vibrations of the shell or casing cause audible sounds which are collectively referred to as shell noise.

The elimination of shell noise presents a diificult problem .to manufacturers of mufiiers as shell vibration characteristics which set up the so-called shell noises vary with the types and sizes of. mufiier constructions, the volume and rate of flow of the exhaust gases and the various wave lengths of sound waves entrained in the gas stream.

In certain types or" prior muffler constructions, a double wall shell has been utilized wherein substantial space is provided between the shell walls, the space being packed with asbestos or other resilient, fireproof packing material for the purpose of reducing or damping vibrations of the shell walls. In my prior Patent No. 2,151,084, granted March 21, 1939, there is disclosed a muflier provided with double walls or shells wherein the inner shell is formed with pressed-out spots, or dimples, engageable with the outer shell for the purpose of reducing or minimizing shell noise. The construction disclosed in my prior patent, while effective to reduce shell noise toa certain extent, is not entirely satisfactory under all conditions of operation of an engine.

The present invention embraces the provision, of :a

silencer or muiiier construction embodying a multiplewalled shell or casing construction formed to provide substantial wall-supporting and reinforcing zones between the walls .and forming an air space or spaces for cushioning and efiectively minimizing, reducing or modifying 2,835,336 Patented May 20, 1958 vibratory movements of the shell walls to reduce effectively or eliminate shell noise.

An object of the invention is the provision of a silencer or mufiier construction embodying a double-walled shell of which at least one wall is configurated with elongated, raised or struck-up portions engageable with the other wall of the shell to efiectively maintain the walls in properly spaced relation throughout their contiguous areas, facilitating the maintenance of one or more air chambers or sinuous air spaces between the walls for reducing or modifying vibrations of the shell'walls to a substantially inaudible range.

Another object of the invention is the provision of a doublewalled casing construction for a sound-attenuating instrumentality wherein at least one of the wallsis provided with spaced, linear ridges or raised portions engageable with the other wall whereby the transmission of sound waves set up in the air between the walls is obstructed or interrupted by the linear ridges and shell noise thereby reduced or eliminated.

Another object of the invention is the provision of a silencer or mutiler construction for'use with a moving gas stream wherein the muffler shell consists of double walls, at least one of which is formed with spaced, elongated ridges or raised portions disposed in staggered or oiiset relation engageable with the other wall to provide reinforcement therefor and spaced zones of contact therewith whereby the normal periodicity of vibration of the shell wall construction is altered or modified and audible sounds or shell noise substantially eliminated.

Still another object of the invention is the'provision of a shell construction for a muffler or sound-attenuating device embodying a double wall casing arrangement in which one or both walls may be provided with raised, elongated ridges or portions engageable with the other wall, providing for a rigid construction and which is comparatively inexpensive to manufacture.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, tovarious details of construction and to combinations of parts, elements per se, and to economics of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

Figure 1 is an elevational view partly in section illustrating a muflier construction embodying one form of the invention;

Figure 2 is a transverse sectional view taken substantially on the line 2-2 of Figure 1;

Figure 3 is an enlarged fragmentary isometric view illustrating the form of tubular wall shell construction shown in Figure 1;

Figure 4 is a sectional view similar to Figure 2 show- ;ing a modified form of tubular wall shell construction tially-on the line 7-7-of Figure 6;

Figure 8 is an elevational view partly in section of a portion of a muffler illustratin another form of shell wall configuration;

Figure 9 is a transverse sectional view taken'substantially on the line 99 of Figure 8;

Figure 10 is an elevational view partly insection of a portion of a muffler illustrating still another form of :mufiler shell construction, and

Figure 11 is a transverse sectional view taken substantially on the line 11-11 of Figure 10.

While I have illustrated the several forms of shell construction of my invention as embodied in a type of mufiler or silencer incorporating gas passage tubes arranged in spaced relation and embodying certain forms of sound-attenuating and resonance chambers, it is to be understood that the forms of shell construction may be utilized in other types of silencer or muffler for attenuating sound waves entrained in a moving gas stream.

With particular reference to the form of the invention illustrated in Figures 1 to 3, the sound-attenuating muffler or silencer is provided with a shell or casing formed with double walls comprising, more specifically, an inner shell member or wall 11 and an outer shell member or wall 12, the shell members or walls 11 and 12 being in telescoped relation and formed to generally elliptical or oval configuration in cross section as shown in Figure 2. It is to be understood that other shapes such as circular cross section may be employed if desired. The members 11 and 12 in this form of the invention provide a dual wall construction, the inner and outer members being preferably formed of individual metal sheets coextensively assembled or joined by an overlapping seam construction 14 as shown in Figure 2,the seam extending lengthwise of the shell. If desired, the sheets may be welded at their zones of overlap in lieu of the interlocking seam 14.

The muffier shell construction is provided at its ends with heads or closures 15 and 16 having peripheral flange portions 17 providing recesses into which extend the ends of the shell construction formed by walls 11 and 12. It is to be understood that other suitable means such as welding may be employed for retaining the end heads in position. In the illustrated embodiment, the outer flange 17 on each head is rolled or coined into firm engagement with the exterior shell wall 12 to frictionally secure the head in position.

As shown in Figures 1 through 3, the outer shell or wall 12 is formed with a plurality of longitudinally extending, interrupted or spaced grooves 20 which form on the interior of the shell wall 12 a plurality of spaced ridges or raised portions 21. As particularly shown in Figure 1, the grooves are comparatively narrow, are comparatively short in length and are arranged in rectilinear groups lengthwise of the shell and in lengthwisespaced relation. Transversely of the shell, the groups of grooves 20, forming the ridges 21, are disposed in staggered relation in a manner particularly shown in Figures 1 and 3. The innermost surfaces of the ridges or raised portions 21 engage the exterior surface of the inner shell wall 11. The inner wall 11, through its multi-zoned contact with the raised portions 21, provides an adequate support and reinforcement throughout the entire area between the shell Walls 11 and 12 to assist in reducing shell noise. Through the staggered transverse spacing and arrangement of the raised portions 21, the raised portions provide obstructions or impediments which interrupt or obstruct the transmission of sound waves that may be set up in the air contained between the shell walls and quickly damp out or attenuate such sound waves.

The muffier is formed with an exhaust gas inlet tube 26 and an exhaust gas outlet tube 27 mounted, respectively, in openings formed in the end heads 15 and 16. The inlet tube 26 is telescoped with a gas passage tube 29 and the exhaust gas passage tube 27 is telescoped with a gas passage tube 30, the tubes 29 and 30 being of a similar construction and in transversely spaced relation in the mufiler illustrated in the drawings. The interior of the mutiler is provided with centrally disposed, transverse bafiies 32 and 33 and other bafiies 35 and 36 arranged between the bafile 33 and the end head 16, a similar set of bafiles (not shown) being contained within the opposite end zone of the mufiier. The inlet tube 29 and the 4 outlet tube 30 extend through openings in the centrally disposed battles 32 and 33, those portions of the tubes between'the baflles being provided with a plurality of small openings 38 establishing gas passage means and acoustic couplings between the tubes and between the tubes and the chamber 40 formed by the bafiles 32 and 33.

The baffies 32 and 33 are also provided with flanged openings to receive an intermediate gas passage tube 44, the wall of which is provided with a plurality of small openings 45. Surrounding the tube 44 and spaced therefrom is a tube 48 which is also formed with a plurality of small openings 50 to facilitate the transverse flow of exhaust gases as well as to form acoustic couplings with the chamber 40 formed between bafiles 32 and 33. The annular space formed between the tubes 44 and 48 provides a high-frequency sound-attenuating chamber for damping or attenuating high-frequency sound waves. The baffies 35 and 36 are provided with openings 52 to facilitate the entrance of sound waves into the resonance chambers 54 and 56. The bafiles (not shown) in the opposite end of the mufiler may be of a construction the same or similar to baffies 35 and 36 providing additional resonance chambers in the mutfler.

In the particular construction of gas passage and sound-attenuating means in the muffler as disclosed in Figure 1, the exhaust gas from an internal-combustion engine or other gas stream is conveyed through the inlet tube 26 and tube 29 to the chambers 40 and 58, the latter being formed by baffles 33 and 35. A similar chamber 58 is formed adjacent the left side of baffle 32 as viewed in Figure l. The gas travels transversely through openings 38 in tube 29, openings 45 and 50 in tubes 44 and 48, respectively, and openings 38 in the exhaust tube 30 by way of the chamber 40 to the exhaust outlet 27. Gas may also fiow transversely through the gas transfer chambers 58 disposed adjacent the baffles 32 and 33, respectively. The openings in the walls of the several tubes provide acoustic couplings with the chamber 40 for attenuating sound waves. The chambers 58, 54 and 56 form resonance chambers for also attenuating sound waves of lower frequencies. It is to be understood that the double-walled shell construction of the invention may be used with other arrangements of gas passage tubes and sound-attenuating or resonance chambers without departing from the spirit of the invention.

The general functioning of the muffier is as follows: the stream of exhaust gases from an internal-combustion engine, or other moving gas stream, with which the mufiier may be used enters the mufller through the gas inlet passage 26 and is conveyed to the central zone of the mulfler through the gas inlet tube 29. The major amount of gas then flows laterally through the openings 38 in the wall of the tube 29, through the chamber 40 into the intermediate tube 44 and through openings in the gas passage tube 30 connected with the exhaust outlet 27. The gas may also travel laterally from the open end of the tube 29 through the righthand transfer passage 58 and in a reverse direction through tube 44, thence through the lefthand transfer passage 58 into the gas outlet tube 30.

While some of the gases may circulate in the resonance chambers 54 and 56, no lateral transfer of gases will be afiected in these chambers as the walls of gas passage tubes 29 and 30 are preferably unperforated at the zones of said chambers. The acoustic couplings, provided by the many openings 38, 45 and 50 in the several tubes in the mufller, with the chamber 40 and the resonance chambers 54 and 56 provide effective means for attenuating sound waves entrained in, or set up by, the moving exhaust gas stream. Through this arrangement, a broad range of sound waves is effectively attenuated through the arrangement above-described contained in the interior of the muffier shell construction. It is to be understood, however, that modifications of the sound-attenuating and gas passage tubes and chamber construction may be utilized in the shell construction of the present invention.

"ass-sass The shell arrangement of a muflier is subjected to vibration under the influence of energy of sound waves impinging upon the interior shell wall of the muffler. Such vibrations result in very obnoxious, audible sounds, referred to as shell noise. The double-walled shell construction of the present invention, through the use of the spaced apart ridges in one shell wall engaging the other, forms a reinforced, double-walled arrangement wherein the natural vibration period of each individual wall is modified by contact with the other so that vibrations of the shell wall or walls are substantially reduced or are modified so as to be substantially inaudible with the result that shell noise is eliminated or very effectively reduced. Furthermore, the raised ridges on the shell walls provide abutments or impediments disposed between the walls which interrupt the transmission of sound waves impressed upon the air contained in the space between the shells, a factor which further reduces shell noise.

The ends heads 15 and 16 are secured to the walls of the shell so as to effect a hermetic seal of the air chamber existent between the shell walls so that exhaust gases are not projected into the space between the walls.

A modified form of the double-walled shell construction is illustrated in Figures 4 and 5. In this form of the invention, the inner shell 61 is formed with outwardly extending or projecting ridges 62 of comparatively short length extending longitudinally of the shell construction in spaced apart relation. As shown in Figure 5, each linear group of ridges 62 is arranged in staggered relation with respect to the adjacent group of linear ridges in the same manner as the ridges 21 are arranged in the outer shell wall as shown in Figure 3. The outer shell wall 65, as shown in Figures 4 and 5, is smooth-surfaced. This arrangement performs the function of reducing shell noise in substantially the same manner as the arrangement shown in Figures 1 through 3.

It is to be understood that, if desired, the inner shell 61 and the outer shell 65 each may be provided with projecting ridges in interengagement with a surface of the other shell without departing from the spirit of the invention.

Another form of the invention is illustrated in Figures 6 and 7. In this form, the exterior shell wall 70 is pro vided with a series of groups of ridges 72 formed by depressions 73 impressed in the exterior surface of the shell wall. The ridges '72 contact or engage the inner shell wall 74 in the manner shown in Figure 7 to accomplish the functions of the invention as hereinbefore described. As shown in Figure 6, the ridges are of comparatively short length and are spaced lengthwise of the shell construction. Peripherally of the shell the ridges are arranged in circumferential groups in which the individual ridges are in aligned relation circumferentially of the shell. By this arrangement, the ridges establish successively spaced linear zones of engagement or contact between the shellsproviding a satisfactory reinforcing for the shells.

Another form of the invention is illustrated in Figures 8 and 9. In this form, one of the shell walls is formed with a mesh-like configuration of raised portions to establish engagement between the shells at spaced Zones. In the illustration, the outer shell 80 is formed with a plurality of parallel depressions 82 arranged diagonally of the shell intersecting a second series of depressions 84 in diagonal arrangement to form intersecting inwardly extending projections on the outer shell. The intersections of the recesses $2 and $4 form diamond-shaped projections 86 on the interior of the shell 80 as shown in the drawings. The ridges or projections 86 are of a height to engage the exterior surface of the inner shell 88 providing a reinforced, double-walled shell construction. The ridges 86, formed by the group of diagonally arranged recesses 82 and 84, may be formed by rolling a sheet of metal through a suitable impression roll or coining device for impressing the recesses in the sheet. The construction shown in Figure 8 provides an extremely rigid arrange ment and, moreover, forms individual air cells or chambers 90 of diamond shape or configuration which assist in minimizing shell noise.

Figures 10 and 11 illustrate another form of the invention wherein the outer shell 92 is formed with aplurality of circumferentially spaced, serpentine-like depressions 94, forming inwardly extending, nonrectilinear ridges 95 which engage the adjacent surface of the inner wall 96 of the mother shell construction. In this arrangement the serpentine-like ridges engage the inner shell and provide a substantially rigid construction of double-walled shell. The longitudinal disposition of the ridges 95 forms longitudinally extending air cells or chambers 98 which assist in reducing shell noise by preventing transmission of vibrations through the air spaces between the shell walls.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than is herein disclosed, and the present disclosure .is illustrative merely, the invention comprehending all formed with spaced elongated ridges projecting toward and having rectilinear contact with the other of said walls at zones spaced longitudinally and circuniferentially of the shell construction, closures secured at the ends of the walls of the shell construction, said ridges forming obstructions to oppose transmission of sound waves in the air contained between the walls of the shell construction, the space between said shell walls being out of communication with exhaust gases passing through the muffler.

2. A mufiler for use with the exhaust system of an internal-combustion engine including a shell construction having a pair of spaced walls, one of said walls being formed with spaced elongated ridges projecting toward and in contact with the other of said walls at zones spaced longitudinally of the shell construction, the peaks of the ridges being in rectilinear engagement with the and in contact with the other of said walls in rectilinear zones spaced circumferentially of the shell construction, said ridges being of comparatively short length, closures secured'at the ends of the walls of the shell construction, said ridges forming obstructions to interrupt sound waves in the air contained between the walls of the shell construction, the space between said shell walls being out of communication with exhaust gases passing through the muffler.

4. A muffler for use with the exhaust system of an internal-combustion engine including a shell. construction having a pair of spaced walls, one of said walls being formed with groups of rectilinear ridges, the ridges of each group being aligned lengthwise of the shell construction and the groups of ridges being peripherally spaced around the wall, the peaks of the ridges being in rectilinear contact with the other of said walls, said ridges forming obstructions to reduce transmission of sound waves set up in the air contained in the space between the shell walls, and closures secured at the ends of the Walls of the shell construction.

5. A mufiier for use with the exhaust system of an internal-combustion engine including a shell construction having a pair of spaced walls, one of said walls being formed with groups of rectilinear ridges, the ridges of each group being aligned lengthwise of the shell construction and the groups of ridges being spaced peripherally on the wall, the ridges of alternate groups being in staggered relation peripherally of the shell construction, the peaks of the ridges being in rectilinear contact with the other of said walls, said ridges forming obstructions to reduce transmission of sound waves set up in the air in the space between the shell walls, closures secured at the ends of the walls of the shell construction, the space between the shell walls being out of communication With the exhaust gases passing through the muffler.

6. A muffler for use with the exhaust system of an internal-combustion engine having a shell comprising a pair of tubular sheet metal elements peripherally spaced apart, a closure for each end of the shell, gas inlet and outlet passages formed in said closures respectively, a plurality of partitions disposed transversely in said shell and forming with the inner tubular element a plurality of sound-attenuating chambers, and gas passage tubes disposed in said shell for conveying gases therethrough, one of said elements being formed with longitudinally and circumferentially spaced groups of ridges projecting from a surface of the element, the peaks of said ridges being in engagement with the other of said elements in rectilinear Zones whereby one element is supported throughout substantially its entire area by the ridges on said other element, said ridges forming abutments in the air space between said elements for minimizing transmission of sound Waves in the space between said elements.

7. A mufiler for use with the exhaust system of an internal-combustion engine including a casing formed with a pair of spaced walls, one of said walls being formed with a plurality of elongated ridges spaced longitudinally and peripherally of the casing, said ridges projecting toward the other of said walls and extending into the space between said walls and establishing obstructions in said space interrupting the transmission of sound waves set up in said air space by impingement of sound waves upon the inner wall, the peaks of said ridges being in rectilinear contact with the other of said Walls, said ridges forming reinforcing means for the other of said walls to reduce vibratory movements thereof whereby shell noises are substantially reduced.

8. A muflier for use with the exhaust system of an internal-combustion engine including a casing formed with a pair of spaced walls, one of said walls being formed with a plurality of ridges of elongated nonrectilinear shape, said ridges projecting toward the other of said walls at circumferentially spaced zones, said ridges extending into the space between said walls and establishing obstructions in said space interrupting the transmission of sound Waves set up in said air space by impingement of sound waves upon the inner wall, the peaks of the elongated ridges being in linear contact with the other of said walls, said ridges forming reinforcing means for the other of said walls to reduce vibratory movements thereof whereby shell noises are substantially reduced.

9. A mufiier for use with the exhaust system of an internal-combustion engine including a casing formed with a pair of spaced walls, one of said walls being formed with a plurality of circumferentially spaced ridges of elongated curvilinear shape, said ridges projecting toward the other of said walls, said ridges extending into the space between said walls and establishing obstructions in said space adapted to reduce the transmission of sound waves set up in said air space by impingement of sound waves upon the inner wall, the peaks of the ridges being in linear contact with the other of said walls, said ridges forming supporting means for the other of said walls to reduce vibratory movements thereof whereby shell noises are substantially reduced.

10. A muflier for use with the exhaust system of an internal-combustion engine including a casing formed with a pair of spaced walls, one of said Walls being formed with a group of ridges disposed in substantially parallel relation and diagonally arranged with respect to the longitudinal axis of the casing, said ridges projecting toward a surface of the other of said walls, the peaks of the ridges engaging the surface of the other of said Walls in linear zones, said ridges forming reinforcing means for said other wall to reduce vibratory movements thereof whereby sound waves entrained in the exhaust gas stream impinging upon the inner wall are substantially damped out and shell noise thereby substantially reduced.

11. A muffler for use with the exhaust system of an internal-combustion engine including a casing formed with a pair of spaced walls, one of said walls being formed with a group of ridges disposed in substantially parallel relation and diagonally arranged with respect to the longitudinal axis of the casing, a second group of ridges arranged in substantially parallel relation and diagonally disposed with respect to and intersecting the first-mentioned group of ridges, the ridges of both groups projecting toward a surface of the other of said walls, the peaks of the ridges engaging the other of said walls in linear zones, said ridges forming reinforcing means for said other wall to reduce vibratory movements thereof whereby sound waves entrained in the exhaust gas stream impinging upon the inner wall are substantially damped out and shell noise thereby substantially reduced.

12. A mufiler for use with the exhaust system of an internal-combustion engine having a shell comprising a pair of tubular sheet metal elements peripherally spaced apart, a closure for each. end of the shell, gas inlet and outlet passages formed in said closures respectively, one of said elements being formed with a plurality of comparatively short linear ridges projecting from a surface of the element, said ridges being spaced lengthwise of the shell, the space between successive ridges being less than the length of a ridge, the peaks of said ridges being in engagement with the other of said elements in linear zones whereby one element is supported throughout substantially its entire area by the ridges on said other element, said ridges forming abutments in the air space between said elements for minimizing transmission of sound waves in the space between said elements.

References Cited in the file of this patent UNITED STATES PATENTS 1,186,572 Guibert June 13, 1916 1,701,397 Trumble et al. Feb. 5, 1929 2,151,084 Deremer Mar. 21, 1939 2,652,128 Cary Sept. 15, 1953 2,661,073 Deremer Dec. 1, 1953 FOREIGN PATENTS 8,529 Australia July 26, 1928 

